Polycarbonates which are used in engineering applications are tough, relatively brittle in thick parts, difficult to process, and expensive. It is desirable that polycarbonates be modified without reducing their toughness by blending them with less expensive polymers, and that their processability and brittleness be improved.
Thus the prior art has modified polycarbonates with polybutadiene rubber grafted to styrene and acrylonitrile or polybutadiene grafted to styrene and methylmethacrylate (MMA) with various combinations of styrene and acrylonitrile copolymers, and ABS. Examples of such alloys may be found in U.S. Pat. Nos. 3,852,394, 3,873,641, 4,461,868, 4,683,265, and 4,806,593 which patents are incorporated herein by reference.
The prior art gives little or no guidance as to the efficacy or practicality of untried alloys or how to select them from the myriad of possibilities available.